In recent years there has been expanding use of network systems in which a plurality of electronic computers are interconnected. Companies in general have come to use such network systems in business operations. Each company is engaged in efforts to manage the handling and flow of business data. When important data within a company is printed and then is leaked outside the company, such consequences as lowered public standing of the company, influencing the company's stock price, result. Particularly in industries in which the personal information of customers is handled, there are serious problems of loss of customer trust; in light of the possibility of carelessness or illicit operations on the part of employees, external intruders or others, it is vital that the type of files being printed from electronic computers be monitored and managed.
The following technology has been disclosed as means of controlling printing to printing devices from electronic computers. In Patent Document 1, when a printer is accessed from an application program operating on a computer and printing is performed, the act of printing is detected by a common interface driver, and control is executed to permit or forbid printing by referencing the file and data which is to be printed.
More specifically, when a printer is accessed by an application program, the computer is controlled and the a spooler of the operating system which is running the application program operates. Access is detected through an event which occurs when this spooler operates. The common interface driver controls data output to the printer according to control conditions registered in advance in a control condition database.    Patent Document 1: International Patent Publication No. 2004/077287